ELECTRICAL LOAD CONTROL MONITORING UNITS (LCMUs)

Abstract

A method of power switching includes receiving a command from an external aircraft controller to power an aircraft load from an aircraft voltage bus. The method includes in response to the command from the external aircraft controller, controlling a relay to connect or disconnect an aircraft voltage bus from an aircraft load. Controlling the relay includes current monitoring the relay and voltage monitoring the relay power switching. The method can include receiving temperature feedback indicative of temperature of the relay, and using the temperature feedback for at least one of controlling the relay and/or prognostic and health monitoring. The method can include outputting feedback to the external aircraft controller relating to status, operation, and health of the relay.

What is claimed is: 
     
         1 . A system comprising:
 a load control monitoring unit (LCMU), wherein the LCMU includes a controller operatively connected for input and output with an aircraft interface and a coil driver operatively connected to be controlled by the controller;   a voltage sensor operatively connected to a voltage bus side of a main switching device of a relay and to the controller to provide voltage feedback to the controller indicative of current in the voltage bus side of the main switching device,   wherein the controller is configured to control the main switching device, and to provide overvoltage protection for the relay.   
     
     
         2 . The system as recited in  claim 1 , wherein the relay operatively connected to the LCMU for controlling connection and disconnection of an aircraft voltage bus to and from an aircraft load, wherein the relay includes a coil operatively connected to be powered by the coil driver, wherein the controller is configured to control the coil driver to control the main switching device, wherein an auxiliary switching device is operatively coupled to be actuated by a magnetic field from the coil, and wherein the main switching device is operatively connected to be actuated by the magnetic field from the coil, wherein the auxiliary switching device is operatively connected to the controller to provide feedback indicative of position of the main switching device, and further comprising:
 a current sensor operatively connected to a load side of the main switching device and to the controller to provide current feedback to the controller indicative of current in the load side of the main switching device, wherein the controller is configured to open the main switching device of the relay for overvoltage (OV) protection in the presence of unacceptable voltages sensed by the voltage sensor.   
     
     
         3 . The system as recited in  claim 1 , wherein the controller is configured to use the voltage feedback to monitor for under-voltage for prognostic and health monitoring (PHM). 
     
     
         4 . The system as recited in  claim 1 , wherein the controller is configured to use the current feedback to open the main switching device of the relay for overcurrent (OC) protection in the presence of unacceptable current sensed by the current sensor. 
     
     
         5 . The system as recited in  claim 1 , further comprising a temperature sensor operatively connected to the relay and to the controller to communicate temperature feedback to the controller indicative of temperature of the relay, wherein the controller is configured to use temperature feedback for prognostic and heath monitoring (PHM). 
     
     
         6 . The system as recited in  claim 1 , further comprising the aircraft voltage bus, wherein the aircraft voltage bus is operatively connected to the voltage bus side of the main switching device. 
     
     
         7 . The system as recited in  claim 6 , further comprising the aircraft load operatively connected to the load side of the main switching device, wherein the controller is configured to:
 control the coil driver to close the main switching device to connect the aircraft load to be supplied by the aircraft voltage bus in a first position of the main switching device, and   control the coil driver to open the main switching device to disconnect the aircraft load from being supplied by the aircraft voltage bus in a second position of the main switching device.   
     
     
         8 . The system as recited in  claim 1 , wherein the coil driver is configured to: receive a command from the controller to close the main switching device, and in response to issue a first pulse width modulation (PWM) current to the coil for a first period of time for closing the main switching device followed by a second period with a second PWM current for holding the main switching device closed, wherein the second PWM current has a lower duty cycle than the first PWM current. 
     
     
         9 . The system as recited in  claim 8 , wherein the controller is configured to adjust current levels during the first period based on temperature feedback. 
     
     
         10 . The system as recited in  claim 1 , wherein the coil is a pull-in coil and wherein the relay includes a holding coil operatively connected to the coil driver and to the main switching device, wherein the coil driver is configured to:
 receive a command from the controller to close the main switching device, and in response to drive current to the pull-in coil and to the holding coil for a first period of time for closing the main switching device, followed by depowering the pull-in coil and driving current only to the holding coil for holding the main switching device closed.   
     
     
         11 . The system as recited in  claim 10 , wherein the controller is configured to adjust current levels during the first period based on temperature feedback. 
     
     
         12 . The system as recited in  claim 1 , further comprising a communication bus operatively connecting the controller to an external aircraft controller for control and status of the relay. 
     
     
         13 . The system as recited in  claim 1 , wherein the controller is configured to count operating power cycles of the relay for prognostic and health monitoring (PHM). 
     
     
         14 . A method of power switching comprising:
 receiving a command from an external aircraft controller to power an aircraft load from an aircraft voltage bus; and   in response to the command from the external aircraft controller, controlling a relay to connect or disconnect the aircraft voltage bus from the aircraft load, wherein controlling the relay includes current monitoring the relay and voltage monitoring the relay.   
     
     
         15 . The method as recited in  claim 14 , wherein controlling the relay includes receiving voltage feedback indicative of voltage across the relay and controlling the relay to open and disconnect the aircraft load from the aircraft voltage bus as needed for overvoltage (OV) protection. 
     
     
         16 . The method as recited in  claim 15 , further comprising communicating voltage data to the external aircraft controller for prognostic and health monitoring (PHM). 
     
     
         17 . The method as recited in  claim 14 , wherein controlling the relay includes receiving current feedback indicative of current passing through the relay from the aircraft voltage bus to the aircraft load, and controlling the relay to open and disconnect the aircraft load from the aircraft voltage bus as needed for overcurrent (OC) protection. 
     
     
         18 . The method as recited in  claim 17 , further comprising communicating current data to the external aircraft controller for prognostic and health monitoring (PHM). 
     
     
         19 . The method as recited in  claim 14 , further comprising receiving temperature feedback indicative of temperature of the relay, and using the temperature feedback for at least one of controlling the relay and/or prognostic health monitoring. 
     
     
         20 . The method as recited in  claim 14 , further comprising outputting feedback to the external aircraft controller relating to status, operation, and health of the relay.